Production of isobutane



Patented May 4, 1943 1 UNITED. STATES PAT mlgorriws J PRODUCTION or ISOBUTANE Vladimir N. Ipatiei! and Herman mantra, o

Ill., assignors to Universal Oil Products ,company, Chicago, 111., a corporationot Delaware No Drawing. Application September 3|), 1936,- v Serial No. 103,383. Divided and this application March-16, 1942, Serial No. 4,903

5 Claims. (crest- 683.5).

This is a division of our co-pending application Serial No. 103,383, filed September30, 1936.

This invention relates particularly to the treatment of butane of normal or straight-chain structure. In a more specific sense, the invention is concerned with a process whereby normal butane is converted into isobutane, the process involving the use of special catalysts and particular conditions of operation which favor the isomerization reactions so that relatively high yields of the iso-compoundare produced.

Since the invention is concerned principally with the two 4-carbon atom paramn hydrocarbons and their transformatiomone into the other,

the following table is introduced to indicate the structure and the principal. physical characteristics of these two compounds:

Properties of butanes titles in the oil refining industry; They occur in substantial amounts in natural gases (in which the normal compound usually predominates), in

refinery gases which are evolved from-crude petroleum storage tanks, and in the primary distillation of crudes, and they are also present in considerable percentages in the gases produced incidental to cracking heavy petroleum fractions for the production of gasoline. In the case of cracked gas mixtures the relative proportions of iso and normal butanes vary, but the ratio of the iso to the normal compound is as a rule considerably higher than in natural Butanes may be considered as more or less marginal compounds in respect to their desirability in ordinary gasoline, that is, a certain percentage of them is essential for sufficient vapor pressure to insure ease in starting, while an ex- 5 cess tends to produce vapor lock. For these reasons the total percentage ore-carbon atom hydrocarbons is commonly adjusted in conjunction" with the boiling range and vapor pressure of the other gasoline components to produce a gasoline 5 of desirable starting characteristics; "according to "seasonaldemands.

The butanes at the present time bearaiurther important relationshiptofioil refining in that {their excess production is being utilized as a source of,gasoline either by ordinary thermal cracking or by special catalytic' dehydrogenation processes i'ollowed by polymerization in which catalysts may or "may not be used; {investigations have shown-that.;isobutane is considerablymore amenableito cracking-and dehydrogenation, both'with and without catalysts, than the normal compound. Considering the corresponding mono-olefins, the normal butenes are considerably more difficult to, polymerize, either thermally or catalvtically, than iso-hutene, and

7 it is found also that the octenes representing the dimers oi the isobutene are of higher antiknock value than those from n-butenes which-holds also for the octanes produced by hydrogenation.-

- It is, therefore, of considerable importance at the presenttime to convert as much as possible of the normal butane production into iso-butane,

I and the present inventionis especially concerned 25 with a process ior accomplishing'thisobject.

In one specific embodiment the present invention comprises the treatment. of normal butane for the isomerization thereof into isobutane with catalysts comprising essentially metallic halides at elevated temperatures and superatmospheric pressures.

In apreferred embodimentthecatalysts comprise essentially heavy metal chlorides and hydrogen halides, r a v We have determinedthat by-they use of the class of catalysts mentioned, and particularly by the convenient use of considerable superatmospheric pressure normal butane may be converted into'iso-butane with a yield of as high as to Evidentlythe useof superatmospheric pressures of the order of v10 to 50 atmospheres at temperatures of'l50" C.,and higher, besides depressing the volatilization of granular: catalysts tends also to depress. numerous undesirable side 45 reactions which would result in the formation of hydrogen and low molecular weight hydrocarbons so that .the reaction proceeds more or less inone direction untilan equilibrium is established. Q

There are severaLalternative catalysts which maybeemployed in accomplishing the present isomerization reaction and, while they may be used more or less interchangeably, some are more e'ilective-than others and it is not intended to inier that they are eq-uivalenti Among the comstantially no corrosion case such compounds chloride and stannic chloride. Treatment of the pounds which may be employed may be mentioned alumimnn chloride, zinc chloride, iron chloride, zirconium chloride, stannic chloride and boron fluoride. Experiments have indicated that best results are obtained when a minor percentage of a hydrogen halide is present in the reactions along with these compounds. Some 01 the compounds may be employed either in the dry state or in aqueous solution with suitable modifications or operating conditions. In the case of such compounds as aluminum chloride, which readily sublimes, stannic chloride, which boils at 114? C., and boron fluoride, which is normally gaseous, these are most conveniently employed in the anhydrous condition, the hydrogen halides, suchas for example hydrogen chlorideor hydrofluoric acid, being separately introduced in the gaseous state. 'There will be some variations in the relative amounts of metal salts and hydrogen halides used at optimum treating conditions, but the determination of thebest .ratics is somewhat a matter of experiment.

Thepro'cessmay be operated under batch or continuous conditions. Choosing aluminum chloride and hydrogen chloride as example or jointly used catalytic materials, batch operations may be conducted 7 by separately adding aluminum chloride, hydrogen chloridev and normal butane to a closed 'pressurecontainer,faiter.which the container is agitateddr the contents stirred mechanically, while 'the temperature and pressure are raised by the application or externalheat to produce a temperature correspon ng to maximum production of continuous manner.

the butane may. be pumped element at a iv n the iso-compound.* This type i or operation is better adapted to small scale pro; duction, and plants of considerable capacity are" 'conmate. ranges previouslyspecifled-and reaction, brought aboutalong; the line of flowbythe separate or joint injection of proportioned amounts,

of metal salts and hydrogen ample of this type of operation being the comblnation or aluminum chloride and hydrogen chloride or boron fluorideand' hydrogen fluoride.

halides, the best ex In the absence of moisture there will be subwhen using these substances. After passage through the heating element the reactants may be passed to enlarged in-' sulated chambers for the completion or the desired isomerization and the-total products subsequently fractionated to recover catalysts and separate the normal and iso-butanes, after which the normal compound may be recycled for rur-v ther treatment.

Continuous operations may also be conducted by passing normal butane mixed with a hydrogen halide through beds of heated, granular catalyst, which may comprise any of the solid salts mentioned, either alone or mixed with carrying or spacing materials of a relatively inert character. This type or operation is readily utilizable in the as zinc chloride, iron products in these cases will involve merely the condensation of the hydrocarbon products and the recycling or the hydrogen halides ior iurther The following examples are introduced to indicate in a general way the nature of the results obtainable by the use of the process, though they are not introduced with the intention or correspcndingly limiting the scope or the invention.

' by weight of normal gas were introduced.

'found that 'the hydrocarbons peratureof approximately 200 downwardly throughthe contact mass under a -1 pressure'oi approximately 30 atmospheres. Ap-

proximately 60% sulated reaction Example I parts .by weight or normal butane, 20 parts by weight of aluminum chloride and 2 parts by weight 01 hydrogen chloride were introduced under a pressure of about five atmospheres into a pressure vessel. which was then rotated and heated for twelve'hours at an average temperature of C -the maximum pressure developed being about 30 atmospheres. After the bomb was cooled the hydrocarbons were released and fractionated and it was found that they consisted of 66.5% of iso-butane and 31.9% of normal butane. This indicatesflthat the equilibrium under these conditions is considerably in favor of iso-butane.

E:rample II In this operation normal butane was passed through a tubular heating element and then into an enlarged reaction chamber, into which sublimed aluminum chloride and hydrogen chloride A pressure of about 25 to 30 atmospheres and a temperature of C. were maintainedon the reaction vessel, after which the reaction products were separated and it was consisted of about 63% iso-butane and 32% normal butane. This indicates a selective conversion of the normal butane into iso-butane under these conditions.

I s Example 111 In this case the catalyst employed was a compositej consisting oiabout 50 parts by weight of ground pumice and 50 parts by weight or substantiallyanyhdrous zine chloride. This material was placed in a vertical cylindrical reaction 'chamber'whioh' was insulated to conserve heat and the normal butane was preheated to a tem- C. and passed is'o-butane and 30% normal butane were found in the reaction products, the remaining "10% comprising lighter fixed gases and other reaction products.

' Example IV I The 'catalytic materials employed in this case consistedo! boron fluoride and hydrogen fluoride.

Normal butane was preheated to a temperature o1 approxin'iately C. and. passed into an inchamber at the same time as boron; fluoride ed. The reaction chamber was nickel-lined, as this was-fo'und-to further accelerate the isomerization reactions. An analysis of the hydrocarbon products showed that they consisted of approximately 62% by weight of iso-butane and 32% butane, the remaining products being lighter gases and some heavier polymerized products. 1 e

The character the present invention and its value commercially have been shown respectively by the foregoing specification and examples introduced although the proper scope or the invention is not limited in exact correspondenceand hydrogen'fluoride were inject- I tion of iron chloride under conditions and in the presence of an amount of hydrogen chloride such that isomerization-of normal vbutane constitutes the principal reaction of the process.

3. A process for producing 'isobutane which comprises passing normal butane and hydrogen chloride through a reaction zone maintained under isomerizing conditions and containing iron chloride, said conditions and the amount of hydrogen chloride being such that isomerization of normal butane constitutes'the principal reaction oi the process.

' f. A process for producing isobutane from norrnal butane which comprises adding gaseous hydrogen chloride to the normal butane and passing the resulting mixture under isomerizing conditions to a bed of solid carrier material containing iron chloride, said conditions and the amount o; hydrogen chloride being such that isomerization 01. normal butane chloride, said con- 

